I/O 



REGENERATION 



Grafting experiments in planarians have so far been carried out in 

 only the two cases which I have described. In one of these the ante- 

 rior ends of two short pieces of Bipalium kewense were united (Fig. 



50, A). Neither piece produced a 

 head at the region of union. Later 

 the pieces were cut apart by an 

 oblique cut that passed across the 

 line of union (Fig. 50, C), so that 

 each piece retained at its most an- 

 terior end (at one side) a piece of 



\ 



FIG. 51. Two pieces of Bipalium kewense 

 united by posterior ends. Each regen- 

 erated a head at anterior end. 



the other individual in a reversed 

 position. A head developed at the 

 anterior (and lateral) end of each 

 piece, in such a way that a part at 

 least of the small reversed piece 

 was contained in the new head 

 FIG. 5 o. A. Two pieces ot tiipaJtum tewense /p- r O n\ In the other case two 



united by anterior ends. B, C. Later V r J &' -> u > ^ )' 



stages of same. Line in C indicates how pieces of bipalium were United by 



pieces were cut apart. D. Two worms 



produced by these pieces. 



. . r -.-* , 



All drawn to their posterior CUt-SUrfaCCS. Each 



piece produced a new head at its 

 free end, and the pieces greatly elongated, but remained sticking 

 together (Fig. 51). 



A large number of experiments have been made by Joest in graft- 

 ing pieces of earthworms. The cut-surfaces were held in contact by 

 means of two or three threads passing through the body wall of each 

 piece and tied across, so that the pieces were drawn together and 

 held firmly in that position. Joest found that pieces of the same or 

 of different individuals could be united in various ways, and the 

 union become permanent. If the anterior end of one worm is united to 

 the posterior end of the same, or of another worm, a perfect union is 



